Greenfield vs Maintenance: Continuing Work on Existing Projects

// Codebase assessment framework
interface CodebaseAssessment {
  projectId: string;
  assessmentDate: Date;
  overallHealth: 'excellent' | 'good' | 'fair' | 'poor' | 'critical';
  metrics: CodebaseMetrics;
  recommendations: Recommendation[];
  actionPlan: ActionPlan;
}

interface CodebaseMetrics {
  maintainability: number; // 0-100
  testCoverage: number; // 0-100
  documentation: number; // 0-100
  performance: number; // 0-100
  security: number; // 0-100
  technicalDebt: number; // 0-100 (higher = more debt)
  complexity: number; // 0-100
  teamKnowledge: number; // 0-100
}

interface Recommendation {
  category: 'architecture' | 'performance' | 'security' | 'maintainability' | 'documentation';
  priority: 'low' | 'medium' | 'high' | 'critical';
  effort: number; // days
  impact: number; // 0-100
  description: string;
  implementation: string;
}

// Example codebase assessment
const legacyEcommerceAssessment: CodebaseAssessment = {
  projectId: 'ECOMM-LEGACY-001',
  assessmentDate: new Date('2024-01-15'),
  overallHealth: 'fair',
  metrics: {
    maintainability: 45,
    testCoverage: 25,
    documentation: 30,
    performance: 60,
    security: 40,
    technicalDebt: 75,
    complexity: 80,
    teamKnowledge: 35
  },
  recommendations: [
    {
      category: 'maintainability',
      priority: 'high',
      effort: 10,
      impact: 80,
      description: 'Refactor duplicate code in user management modules',
      implementation: 'Extract common functionality into shared services'
    },
    {
      category: 'testCoverage',
      priority: 'critical',
      effort: 15,
      impact: 90,
      description: 'Add comprehensive test coverage for critical paths',
      implementation: 'Implement unit tests, integration tests, and E2E tests'
    },
    {
      category: 'documentation',
      priority: 'medium',
      effort: 5,
      impact: 60,
      description: 'Create comprehensive API documentation',
      implementation: 'Use OpenAPI/Swagger for API documentation'
    }
  ],
  actionPlan: {
    phase1: ['Add test coverage', 'Refactor critical modules'],
    phase2: ['Improve documentation', 'Performance optimization'],
    phase3: ['Security hardening', 'Architecture improvements']
  }
};

// Incremental improvement framework
interface ImprovementStrategy {
  name: string;
  description: string;
  approach: 'incremental' | 'modular' | 'strangler-fig' | 'facade';
  benefits: string[];
  risks: string[];
  timeline: number; // weeks
}

const improvementStrategies: ImprovementStrategy[] = [
  {
    name: 'Strangler Fig Pattern',
    description: 'Gradually replace old system with new system',
    approach: 'strangler-fig',
    benefits: [
      'Low risk of system failure',
      'Continuous delivery of value',
      'Gradual team learning',
      'Client satisfaction maintained'
    ],
    risks: [
      'Temporary complexity increase',
      'Integration challenges',
      'Resource allocation complexity'
    ],
    timeline: 12
  },
  {
    name: 'Modular Refactoring',
    description: 'Refactor system module by module',
    approach: 'modular',
    benefits: [
      'Isolated risk',
      'Clear progress visibility',
      'Team specialization',
      'Incremental value delivery'
    ],
    risks: [
      'Module interface changes',
      'Integration complexity',
      'Timeline extension'
    ],
    timeline: 8
  },
  {
    name: 'Facade Pattern',
    description: 'Create modern interface over legacy system',
    approach: 'facade',
    benefits: [
      'Quick modern interface',
      'Legacy system preservation',
      'Gradual migration path',
      'Client experience improvement'
    ],
    risks: [
      'Technical debt accumulation',
      'Performance overhead',
      'Maintenance complexity'
    ],
    timeline: 4
  }
];

// Incremental improvement implementation
class IncrementalImprovementManager {
  private project: Project;
  private strategy: ImprovementStrategy;
  
  constructor(project: Project, strategy: ImprovementStrategy) {
    this.project = project;
    this.strategy = strategy;
  }
  
  // Plan incremental improvements
  async planImprovements(): Promise<ImprovementPlan> {
    const plan: ImprovementPlan = {
      projectId: this.project.id,
      strategy: this.strategy.name,
      phases: [],
      totalTimeline: this.strategy.timeline,
      successMetrics: this.defineSuccessMetrics()
    };
    
    switch (this.strategy.approach) {
      case 'strangler-fig':
        plan.phases = await this.planStranglerFigPhases();
        break;
      case 'modular':
        plan.phases = await this.planModularPhases();
        break;
      case 'facade':
        plan.phases = await this.planFacadePhases();
        break;
    }
    
    return plan;
  }
  
  // Execute improvement phase
  async executePhase(phaseId: string): Promise<PhaseResult> {
    const phase = await this.getPhase(phaseId);
    const result: PhaseResult = {
      phaseId,
      status: 'in-progress',
      startDate: new Date(),
      deliverables: [],
      metrics: {}
    };
    
    // Execute phase-specific improvements
    for (const task of phase.tasks) {
      const taskResult = await this.executeTask(task);
      result.deliverables.push(taskResult);
    }
    
    // Measure phase success
    result.metrics = await this.measurePhaseSuccess(phase);
    result.status = result.metrics.success ? 'completed' : 'needs-improvement';
    result.endDate = new Date();
    
    return result;
  }
  
  // Monitor improvement progress
  async monitorProgress(): Promise<ProgressReport> {
    const completedPhases = await this.getCompletedPhases();
    const currentPhase = await this.getCurrentPhase();
    
    const report: ProgressReport = {
      projectId: this.project.id,
      completedPhases: completedPhases.length,
      totalPhases: this.project.phases.length,
      currentPhase: currentPhase?.name || 'completed',
      overallProgress: (completedPhases.length / this.project.phases.length) * 100,
      velocity: await this.calculateVelocity(),
      qualityMetrics: await this.measureQuality(),
      teamSatisfaction: await this.measureTeamSatisfaction()
    };
    
    return report;
  }
}

// Knowledge transfer framework
interface KnowledgeTransfer {
  type: 'documentation' | 'pair-programming' | 'code-review' | 'workshop' | 'video';
  topic: string;
  duration: number; // hours
  participants: string[];
  effectiveness: number; // 0-100
}

interface DocumentationStrategy {
  type: 'api' | 'architecture' | 'deployment' | 'troubleshooting' | 'user-guide';
  format: 'markdown' | 'confluence' | 'notion' | 'swagger' | 'video';
  audience: 'developers' | 'clients' | 'support' | 'all';
  maintenance: 'automated' | 'manual' | 'community';
}

const knowledgeTransferStrategies: KnowledgeTransfer[] = [
  {
    type: 'pair-programming',
    topic: 'Legacy system architecture',
    duration: 8,
    participants: ['senior-developer', 'junior-developer'],
    effectiveness: 90
  },
  {
    type: 'workshop',
    topic: 'Database optimization techniques',
    duration: 4,
    participants: ['all-developers'],
    effectiveness: 75
  },
  {
    type: 'documentation',
    topic: 'API endpoints and data flow',
    duration: 2,
    participants: ['all-developers'],
    effectiveness: 60
  },
  {
    type: 'video',
    topic: 'Deployment and troubleshooting',
    duration: 1,
    participants: ['all-developers'],
    effectiveness: 70
  }
];

// Knowledge transfer implementation
class KnowledgeTransferManager {
  private project: Project;
  private team: Team;
  
  constructor(project: Project, team: Team) {
    this.project = project;
    this.team = team;
  }
  
  // Plan knowledge transfer sessions
  async planKnowledgeTransfer(): Promise<KnowledgeTransferPlan> {
    const plan: KnowledgeTransferPlan = {
      projectId: this.project.id,
      sessions: [],
      timeline: 4, // weeks
      successMetrics: this.defineKnowledgeMetrics()
    };
    
    // Identify knowledge gaps
    const knowledgeGaps = await this.identifyKnowledgeGaps();
    
    // Plan transfer sessions for each gap
    for (const gap of knowledgeGaps) {
      const session = await this.planTransferSession(gap);
      plan.sessions.push(session);
    }
    
    return plan;
  }
  
  // Execute knowledge transfer session
  async executeTransferSession(sessionId: string): Promise<TransferResult> {
    const session = await this.getSession(sessionId);
    const result: TransferResult = {
      sessionId,
      participants: session.participants,
      effectiveness: 0,
      feedback: [],
      followUpActions: []
    };
    
    // Execute session based on type
    switch (session.type) {
      case 'pair-programming':
        result.effectiveness = await this.executePairProgramming(session);
        break;
      case 'workshop':
        result.effectiveness = await this.executeWorkshop(session);
        break;
      case 'documentation':
        result.effectiveness = await this.executeDocumentation(session);
        break;
    }
    
    // Collect feedback
    result.feedback = await this.collectFeedback(session);
    
    // Plan follow-up actions
    result.followUpActions = await this.planFollowUpActions(session, result);
    
    return result;
  }
  
  // Monitor knowledge transfer effectiveness
  async monitorKnowledgeTransfer(): Promise<KnowledgeMetrics> {
    const metrics: KnowledgeMetrics = {
      projectId: this.project.id,
      teamKnowledgeLevel: await this.measureTeamKnowledge(),
      documentationCoverage: await this.measureDocumentationCoverage(),
      knowledgeRetention: await this.measureKnowledgeRetention(),
      transferEffectiveness: await this.measureTransferEffectiveness()
    };
    
    return metrics;
  }
}

// Production maintenance management system
export class ProductionMaintenanceManager {
  private assessmentManager: CodebaseAssessmentManager;
  private improvementManager: IncrementalImprovementManager;
  private knowledgeManager: KnowledgeTransferManager;
  
  constructor() {
    this.assessmentManager = new CodebaseAssessmentManager();
    this.improvementManager = new IncrementalImprovementManager();
    this.knowledgeManager = new KnowledgeTransferManager();
  }
  
  // Comprehensive maintenance strategy
  async implementMaintenanceStrategy(projectId: string): Promise<MaintenanceStrategy> {
    // Assess current state
    const assessment = await this.assessmentManager.assessCodebase(projectId);
    
    // Plan improvements
    const improvementPlan = await this.improvementManager.planImprovements(assessment);
    
    // Plan knowledge transfer
    const knowledgePlan = await this.knowledgeManager.planKnowledgeTransfer(projectId);
    
    const strategy: MaintenanceStrategy = {
      projectId,
      assessment,
      improvementPlan,
      knowledgePlan,
      timeline: Math.max(improvementPlan.timeline, knowledgePlan.timeline),
      successMetrics: this.defineSuccessMetrics()
    };
    
    return strategy;
  }
  
  // Monitor maintenance progress
  async monitorMaintenanceProgress(projectId: string): Promise<MaintenanceProgress> {
    const progress: MaintenanceProgress = {
      projectId,
      assessmentProgress: await this.assessmentManager.getProgress(projectId),
      improvementProgress: await this.improvementManager.monitorProgress(projectId),
      knowledgeProgress: await this.knowledgeManager.monitorKnowledgeTransfer(projectId),
      overallHealth: await this.calculateOverallHealth(projectId),
      teamSatisfaction: await this.measureTeamSatisfaction(projectId),
      clientSatisfaction: await this.measureClientSatisfaction(projectId)
    };
    
    return progress;
  }
}